Heterodimeric radiotracer targeting PSMA and GRPR for imaging of prostate cancer—optimization of the affinity towards PSMA by linker modification in murine model

Fanny Lundmark, Ayman Abouzayed, Bogdan Mitran, Sara S. Rinne, Zohreh Varasteh, Mats Larhed, Vladimir Tolmachev, Ulrika Rosenström, Anna Orlova

Research output: Contribution to journalArticlepeer-review

Abstract

Prostate-specific membrane antigen (PSMA) and gastrin-releasing peptide receptor (GRPR) are promising targets for molecular imaging of prostate cancer (PCa) lesions. Due to the heterogenic overexpression of PSMA and GRPR in PCa, a heterodimeric radiotracer with the ability to bind to both targets could be beneficial. Recently, our group reported the novel heterodimer BQ7800 consisting of a urea-based PSMA inhibitor, the peptide-based GRPR antagonist RM26 and NOTA chelator. The study reported herein, aimed to improve the affinity of BQ7800 towards PSMA by changing the composition of the two linkers connecting the PSMA-and GRPR-targeting motifs. Three novel heterodimeric analogues were synthesized by incorporation of phenylalanine in the functional linker of the PSMA-binding motif and/or shortening the PEG-linker coupled to RM26. The heterodimers were labeled with indium-111 and evaluated in vitro. In the competitive binding assay, BQ7812, featuring phenylalanine and shorter PEG-linker, demonstrated a nine-fold improved affinity towards PSMA. In the in vivo biodistribution study of [111 In]In-BQ7812 in PC3-pip tumor-bearing mice (PSMA and GRPR positive), the activity uptake was two-fold higher in the tumor and three-fold higher in kidneys than for [111 In]In-BQ7800. Herein, we showed that the affinity of a bispecific PSMA/GRPR heterodimer towards PSMA could be improved by linker modification.

Original languageEnglish
Article number614
Pages (from-to)1-15
Number of pages15
JournalPharmaceutics
Volume12
Issue number7
DOIs
Publication statusPublished - 2020

Keywords

  • GRPR
  • Heterodimer
  • Molecular imaging
  • Prostate cancer
  • PSMA
  • SPPS

ASJC Scopus subject areas

  • Pharmaceutical Science

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